A Green Method to Determine VUV (185 nm) Fluence Rate Based on Hydrogen Peroxide Production in Aqueous Solution

A mini‐fluidic vacuum ultraviolet/ultraviolet (VUV/UV) photoreaction system (MVPS) was developed in our previous study. Based on the MVPS, a green method to determine VUV fluence rate has been developed using the production rate of H 2 O 2 when water is exposed to 185 nm VUV. The H 2 O 2 production followed pseudo‐zero‐order reaction kinetics well over the first 10 min of VUV/UV exposure. This new method was well calibrated with a standard cis ‐cyclooctene cis–trans photoisomerization actinometer as recommended by the International Union of Pure and Applied Chemistry. The apparent quantum yield for H 2 O 2 production by 185 nm VUV irradiation of water was determined to be 0.024 ± 0.002. As the solution pH increased from 5.0 to 8.0, the H 2 O 2 production rate decreased from 0.83 to 0.40 μ m  min –1 . Dissolved oxygen had a negligible influence on the H 2 O 2 production. This study proposes a novel VUV fluence rate determination method with advantages of nontoxicity, low detection limits, low costs and convenience, and it can be used as a good alternative to traditional actinometers.